The invention relates to a recording and/or playback unit for magnetic tape housed in a cassette and capable of being transported out of it. A cassette holder for holding and displacing a cassette is movable between a loading position, in which the cassette can be inserted into the cassette holder, and an opertional position, in which the cassette occupies an operational position. A tape threading device for drawing the magnetic tape out of the cassette when in its operational position and for wrapping it around a magnetic tape scanning device is movable between an unthreaded position, in which it engages behind the magnetic tape housed in the cassette, and a threaded position, in which it holds the magnetic tape wrapped around the scanning device after it has been transported out of the cassette. At least one tape run operating device carries out at least one tape run function with the cassette in its operational position, and is movable between at least two operational positions. In at least one of its two operational positions it effects the tape run function. A differential gear which can be driven in opposed directions of rotation by a motor has at least two outputs by means of which the tape threading device and the tape run operating device are movable via at least one of its outputs.
Such a unit has been proposed in EP-A-O No. 057921, to which U.S. Pat. No. 4,491,885 corresponds. This prior art unit has a differential gear with two outputs. Via one output the tape threading device of the unit is movable between its unthreaded position and its threaded position. The tape threading device consists essentially of two concentric, superposed rings which can be driven via the one output of the differential gear. The rings enclose a drum-shaped scanning device for the magnetic tape and carry the tape guides by means of which, when the rings are displaced from their unthreaded position to their threaded position, the magnetic tape can be transported out of the cassette and wrapped around the scanning device. Via the other output of the differential gear a displacement component constructed as a slide can be driven. When the tape threading device is in its unthreaded position this displacement component is movable via the other output between a neutral position and an intermediate position, in which the displacement component can be stopped and in which the tape threading device is movable via the one output of the differential gear between its unthreaded position and its threaded position. When the tape threading device is in its threaded position, the displacement component is movable via the other output between its intermediate position and three displacement positions. By displacing the displacement component between its neutral position and its intermediate position a movable unit device can be displaced. This unit device has a multi-arm locking lever movable between a release position and a locking position, and a spring loading the locking lever in the direction of its locking position. In its locking position the locking lever locks the cassette holder by means of a lever arm and operates a switch by means of a different level arm. When the displacement component is displced between its intermediate position and its three displacement positions, several tape run operating devices are movable by means of the displacement component, which tape run operating devices are provided for the purpose of effecting several tape run functions, such as "normal forward", "fast forward", "fast rewind" and "stop" when the cassette is in its operational position.
These tape run operating devices comprise a pinch roller device by means of which, in the "normal forward" tape run function, a pinch roller can be pressed against a tape drive shaft for driving the magnetic tape at a constant rate of travel; a spool disc drive device by means of which, in the "normal forward", "fast forward" and "fast rewind" tape run functions, the spool discs, which can be brought into drive linkage with the spools housed in the cassette and whose purpose is to wind the magnetic tape onto one of the two spools, can be driven; a spool disc braking device by means of which, in the "stop" tape run function, the spool discs can be maintained stationary so as to prevent them from rotating undesirably and which, in the "normal forward", "fast forward" and "fast rewind" tape run functions as well as when the magnetic tape is being threaded and unthreaded by means of the tape threading device, is lifted so as to release the spool discs; a tape tension adjustment device, which has a tape tension sensor which can be brought into operative linkage with the magnetic tape and by means of which tape tension sensor, in the "normal forward" tape run function, the tape tension of the magnetic tape driven by means of the drive shaft can be adjusted. The cassette holder is displaced manually in the prior art unit, whereby to displace the cassette holder from its loading position to its operational position it must be pressed down manually, and to displace it in the reverse direction from its operational position to its loading position a displacement device acting upon the cassette holder is operated by hand.
The prior art unit utilizes the differential gear to displace a series of movable unit devices. A disadvantage of the prior art unit, however, is that the cassette holder, which likewise represents a unit device, has to be displaced manually.